In general, a lithographic printing plate is formed from a lipophilic image area for accepting ink and a hydrophilic non-image area for accepting dampening water in a printing process. Lithographic printing is a printing process in which the property of water and printing ink repelling each other is utilized so as to cause a difference in ink attachment on the surface of a lithographic printing plate with a lipophilic image area of the lithographic printing plate as an ink-accepting area and a hydrophilic non-image area as a dampening water-accepting area (non-ink-accepting area), and after inking only the image area ink is transferred to a printing substrate such as paper.
In order to make this lithographic printing plate, a lithographic printing plate precursor (PS plate) formed by providing a lipophilic photosensitive resin layer (photosensitive layer, image recording layer) on a hydrophilic support is widely used in the art. A lithographic printing plate is usually obtained by a process in which, after the lithographic printing plate precursor is exposed through an original image such as a lith film, an area that becomes an image area of the image recording layer is made to remain, and unwanted image recording layer other than this is removed by dissolving using an alkaline developer or an organic solvent to thus form a non-image area in which the surface of the hydrophilic support is exposed.
In this way, in the conventionally known plate-making process of a lithographic printing plate precursor, after the exposure as described above, a step of removing unnecessary image recording layer by dissolving, for example, with a developer is required, but from the viewpoint of the environment and safety carrying out processing with a developer that is closer to neutral or reducing the amount of liquid waste are issues. In particular, since in recent years the disposal of liquid waste discharged accompanying wet treatment has become a great concern throughout the industrial world from the viewpoint of consideration for the global environment, the demand for a solution to the above-mentioned issues has been increasing more and more.
On the other hand, digitization techniques involving electronically processing, storing, and outputting image information by computer have spread widely in recent years, and various new image output methods used with such digitization techniques have been put into practical use. Accompanying this, a computer-to-plate (CTP) technique in which a lithographic printing plate is produced directly without a lith film by carrying digitalized image information in highly convergent radiant rays such as laser light and scanning and exposing a lithographic printing plate precursor with this light has been attracting attention.
JP-A-11-65126 (JP-A denotes a Japanese unexamined patent application publication) for example proposes a development method in which processing is carried out using a developer comprising an alkali metal carbonate and hydrogen carbonate, the developer having a pH of 8.5 to 11.5 and a conductivity of 3 to 30 mS/cm.
Furthermore, an example of EP-A-1868036 describes processing using a processing liquid comprising a water-soluble polymer compound and having a pH of 11.9 to 12.1.
Published Japanese translation 2007-538279 of a PCT application describes processing using a processing liquid comprising a water-soluble polymer compound and having a pH of 3 to 9.